Molecular biology is having a major impact in all areas of biological research. However, rather than being regarded as a separate discipline it should be seen as an extension to our existing repertoire of techniques, enabling us to study biological mechanisms at the whole organism, tissue, cellular and now at the molecular level. This volume presents some of the recent advances which have been made in understanding fundamental biological mechanisms in aquatic organisms by the application of molecular biology techniques.

In spite of homeostatic mechanisms, cellular environmental changes tend to be more extreme in aquatic animals as they cannot avoid external environmental changes such as temperature or salinity by simple behavioural means. The first four and the final chapter of this volume describe some of the recent advances made in understanding how adaptation to the environment is achieved at the level of gene expression. The first chapter (Cheng) describes how Antarctic notothenioid species of fish have adapted to their extremely cold environment by the production of antifreeze glycopeptides and provides new insights at the genomic level as to how heterogeneity of the antifreeze glycopeptides has arisen. In addition to long-term adaptation, some species of fish need to adapt to more acute seasonal changes in temperature. The chapter by Tiku et al. describes how the lipid composition of the cell membrane in carp is controlled by desaturases in response to cold temperature exposure, demonstrating a fascinating situation where transcription of a gene is increased by a decrease in the environmental temperature.